Pancreatic replacement enzymes have been used for treatment of cystic fibrosis since shortly after the disease was first described in 1938. These enzymes were derived from "food" and thought to be intrinsically safe. In recent years very high dose enteric coated preparations were introduced and allowed production of very high-dose capsules. Some CF patients who took very high doses developed severe colonic strictures and many required surgery. With this occurence of a new major toxicity the FDA reviewed the status of these drugs and removed the very high- dose preparations from the market and mandated all other pancreatic enzymes be processed as new drugs. This study is one of many which are now necessary to establish the efficacy of pancreatic enzymes for treatment of CF. The specific aim is to compare fat absorption during a three day period of administration of pancreatic enzyme replacement (Ultrase MT20) with meals with the same patient's data during a 3-day period of administration of a placebo preparation with meals. This study has been completed and data is in analysis.